I just had my battery light come on in my 93 Disco TDI, AFTER I shut down the motor, and of course awoke to a dead battery (which is new). Jumped it and the battery light was only on when I killed the ignition, and would stay lit even with the keys out. Then, the last little drive I had, the battery light came on while driving. Going out to try to troubleshoot today, but thought I'd see if anyone had an idea what the battery indicator is supposed to be indicating? With it coming on when turning the car off, I suspect a short somewhere.

Thanks in advance!

Most likely the alternator is fecked, diode pack has failed.
The battery indicator light on the dash provides the excitation current needed to start the alternator charging, once the alternator starts charging it puts 12 volts on the bulb line so the bulb has 12 volts both ends and therefore goes out.

Datatek said:

Most likely the alternator is fecked, diode pack has failed.
The battery indicator light on the dash provides the excitation current needed to start the alternator charging, once the alternator starts charging it puts 12 volts on the bulb line so the bulb has 12 volts both ends and therefore goes out.

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Ok, but the thing that has me wondering is that the light came on initially when the car was turned off, and it wasn't on while it was running. I checked to see if it would start at that point, and it did. It's like that light being on, or whatever draw it was indicating, killed the battery overnight. And I have had the parking brake light up on occasion, usually when turning, as though the cable is shorting against something when I turn.

Does any of that info change the diagnosis?

garydebergerac said:

Ok, but the thing that has me wondering is that the light came on initially when the car was turned off, and it wasn't on while it was running. I checked to see if it would start at that point, and it did. It's like that light being on, or whatever draw it was indicating, killed the battery overnight. And I have had the parking brake light up on occasion, usually when turning, as though the cable is shorting against something when I turn.

Does any of that info change the diagnosis?

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There is a possibility of a wire short as with the ignition off it should not light.

Datatek said:

There is a possibility of a wire short as with the ignition off it should not light.

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Great, this should be impossible to find. I also had my headlights intermittently going dim until I wiggled some wires, so I would think this is going to be a nightmare.

Is there a standard troubleshooting guide, or best practices for this kind of thing? I was going to start pulling fuses to see if I could nail down the circuit and start investigating from there, starting with the handbrake.

Otherwise I feel like a dealer is just going to say "replace your wire harness", and that sounds really painful.

garydebergerac said:

... the thing that has me wondering is that the light came on initially when the car was turned off,

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another possibility(beside the wiring/short circuit issue which is a good point) is a missbehaveing ignition switch which makes unwanted contact on pos ii after he engine was turned off but this would bring the oil pressure warning too... so if your oil pressure warning is working on ignition before you start the engine but it's not on together with the battery charge warning forget about that.

sierrafery said:

another possibility(beside the wiring/short circuit issue which is a good point) is a missbehaveing ignition switch which makes unwanted contact on pos ii after he engine was turned off but this would bring the oil pressure warning too... so if your oil pressure warning is working on ignition before you start the engine but it's not on together with the battery charge warning forget about that.

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No, just the battery light is on with the ignition off. Or rather was on. I got it jumped and am letting it charge up, and it does seem to be charging, and holding more of a charge. IE the second time i jumped it last night it was closer to starting than the first, and I left it over night and it hadn't completely drained. My volt meter isn't really accurate, hard to tell what the alternator is actually putting out, but it looks like its around 12.

What is weird is that before, the battery light came on when the ignition was off. Now, it comes on when it's running and not when the ignition is off. I am hoping that it will charge itself up, and some moving around of wires I did will take care of it. My plan was going to be to start pulling fuses to see which one would make the battery light go out, but after the second jump last night, that doesn't seem to be happening any more. Oddly, the battery light just came on in the middle of the drive, about halfway home, whereas after the first jump, it wasn't on until I killed the ignition. So yeah, wiring harness and ugh.

then it's quite obvious that it's a problem with the wiring between tha alternator and instrument pack, let fuses alone cos they'll not help in this case cos it's most likely a bad contact on that circuit and the voltage from the alternator on the earth path fails to reach the dash then the warning comes on while driving even though the alternator is charging and when the light was on without engine running the alternator missed the exciter signal and didnt charge enough

you have to see the diagram which wire is connected between the alternator and dash and see where it has problems(i'd help you with pleasure but i dont have D1 diagrams)

Not only a wiring diagram but a Land-Rover Discovery 200 series wiring diagram.

You may have an iffy fusible link, buried within the wiring harness near the battery, depending if your vehicle is pre or post 93MY.
Get yourself a Haynes manual as all the info u need is there and stop guessing and start testing

sierrafery said:

then it's quite obvious that it's a problem with the wiring between tha alternator and instrument pack, let fuses alone cos they'll not help in this case cos it's most likely a bad contact on that circuit and the voltage from the alternator on the earth path fails to reach the dash then the warning comes on while driving even though the alternator is charging and when the light was on without engine running the alternator missed the exciter signal and didnt charge enough

you have to see the diagram which wire is connected between the alternator and dash and see where it has problems(i'd help you with pleasure but i dont have D1 diagrams)

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Well, this is kinda crazy, but while the battery light stays illuminated when its running, it is charging and started this morning no problem. I did have a bunch of wires, unused it seems, fall down near the clutch and had been lazy about pushing them back under the dash. I'm hoping it was just one of these that was shorting out, although that doesn't really explain the light staying on. I do still have all the wires around the fusebox dangling out, and somewhat afraid to push them back in in case the short is there, but seems to be ok. For the moment anyway.